The present invention relates generally to wide area communications systems. More particularly, the present invention relates to a method and apparatus for updating announcement group information within a wide area dispatch system.
In normal processing of a wide area trunked system, communication unit or radio (hereinafter referred to as a xe2x80x9csubscriber unitxe2x80x9d) receives the announcement group ID of its affiliated talkgroup upon performing talkgroup affiliation. However, if the talkgroup to announcement group database in a zone controller is not available for use, the announcement group information cannot be delivered to the subscriber unit. For example, the talkgroup to announcement group database is not available when the database has not been configured by the zone manager. When the database has not been configured, it is not possible for the database to provide information about the announcement group. As a result, when the subscriber unit affiliates to a talkgroup and the talkgroup does not have a preconfigured announcement group, the zone controller will respond to the subscriber unit with an unknown announcement group signal (for example, Null group ID=0). Alternatively, when a site cannot communicate with the zone controller, i.e., it is in site trunking, the zone controller cannot deliver information about the announcement group to the site. A subscriber unit, therefore, may receive an unknown announcement group signal. Both of these situations are problematic because the subscriber unit may not be able to participate in calls for the announcement group that it was intended to receive.
When the zone controller database is configured or the site recovers from site trunking, current systems do not notify the subscriber unit of the updated information about the announcement group. The subscriber unit, therefore, will not be aware of the updated announcement group and will not receive calls it was intended to receive. As a result, there is a need for a method and an apparatus that detects when a subscriber unit is operating with an unknown announcement group signal and in response thereto sends a signal updating the announcement group to the subscriber unit.